In recent years, the increasing volume of waste products and in particular household refuse or garbage has made it necessary to search for solutions permitting the treatment and recycling of these waste products.
It has already been envisaged to employ such waste products as fuel, but the presence in these waste products of a high content of water and incombustible products results in only an insufficient amount of energy.
Indeed, such waste products are constituted by a liquid phase which only contains organic products and a solid phase which contains metallic, mineral and synthetic materials.
One solution consists in compressing these waste products so as to obtain residues which are dry enough to constitute a fuel having acceptable calorific power, fluid substances utilizable, according to their type, in agriculture as ground modifying products or as raw materials from which chemical products may be extracted.
Devices for compressing these waste products are already known and mostly consist of hydraulic presses including a feed zone receiving the waste products to be treated, a press chamber connected to means for recovering the liquid phase, and a chamber for discharging the solid phase located on the downstream side of the press chamber.
This press chamber comprises an inlet opening and an outlet opening and has a section equal to that of a piston of a first jack or ram.
The wall of the chamber comprises a multitude of perforations communicating with a passage for discharging the liquid phase extracted by compression of the waste products.
The outlet opening of the press chamber is usually closed by a plug carried by a rod of a second jack or ram opposed to the first-mentioned jack.
The pistons of the two jacks are movable in a reciprocating manner between a first position of compression of the waste products and discharge of the liquid phase during which the piston of the first jack enters the press chamber and the piston of the second jack closes the outlet opening of the chamber, and a second position of discharge of the solid phase during which the piston of the first jack continues its travel and the piston of the second jack opens the outlet opening of the said press chamber.
This type of press has drawbacks, and in particular presents problems as to the maintenance of the seal between the press chamber and the solid phase discharging chamber.
Indeed, bearing in mind the considerable forces involved when pressing the waste products, the seal is not fully achieved at the outlet opening of the press chamber by the piston of the second jack, so that leakages of liquid may occur and enter the solid phase discharging chamber.
Further, the travel of the piston of the second jack is relatively long. This travel corresponds to a thickness of the solid phase, namely, for an incompressible product, the equivalent of the length of the die, which therefore requires a large volume of oil to actuate this jack.
Bearing in mind this travel, the response time of the second jack is relatively long and rapid rates of operation cannot be obtained.